The present invention relates generally to rotary probe heads. More particularly, the invention relates to rotary probe heads for mounting probes.
A coordinate measuring machine (“CMM”) is used to measure the geometrical characteristics of an object. A CMM may be manually controlled by an operator or it may be computer controlled. The measurements made by a CMM 10 are made by a probe attached to a rotary probe head 100, as shown in FIG. 1A. A variety of probes can be used with CMMs, including mechanical, optical, laser, and white light probes. As shown in FIG. 1A, the rotary probe head 100 is a tool that is commonly mounted on the spindle 50 of a CMM 10 for attaching and moving a probe that measures dimensions of an object. FIG. 1B shows an example of a probe head 100.
Typically, a probe head is actuated to a position and orientation such that the probe can touch and measure an object. In the embodiment shown in FIG. 1B, a touch or stylus probe 110 is attached to the probe head 100. As shown in FIG. 1B, the probe head 100 is mounted on the spindle 50 of a CMM. Servomotors are typically used to actuate and also hold the probe in place while measurements are performed. As shown in FIG. 1B, the probe head 100 has two rotational axes: A and B. In addition to the A and B axes shown in FIG. 1B, some rotary probe heads, such as the rotary probe head 200 shown in FIG. 2, have a third rotational axis, the “C-axis.”
Typically, a rotary probe head can support “stylus” type probes having a mass of about 100 g. Stylus interfaces on rotary probe heads use a kinematically-mounted magnetic interface to attach a stylus probe to the rotary probe head. Laser probes require a different type of interface because the laser probes are much more massive than stylus probes, and a simple magnetic interface is not strong enough to support a laser probe. However, mounting payloads of widely different mass, size, and interface connections on a probe head can be a problem. For example, the “stylus” type probes mentioned above are considered low mass probe tips whereas laser probe heads have much higher mass. If two probes of widely different mass and size are mounted on a probe head, the performance of the probe head may be compromised. Thus, it would be desirable to provide a rotary probe head that can allow for greater flexibility in probe/sensor compatibility as well as improved motor control performance.